[Adoby]

You can create a custom column that store the first (main) author.

Then you can use this as the path in the template when you save to disc.

{#mainauthsort}/{title} - {authors}

You can then order all books using this main/first author and see if there are any variations regarding initials, titles and first name. Use search and replace on Authors to fix.

If you have a very large library (several thousands of books) then this type of custom column will slow down the opening of the library. All the values are set when you open the library, using the list of authors.